NO326239B1 - Threaded container and closure unit - Google Patents

Description

The present invention relates to a threaded container and closure unit, said unit comprising:

a container opening with an inner diameter of at least about 4 cm,,

a closure for said opening, the closure having a base part and a skirt part, a first screw thread on the opening, said first screw thread comprising four or more first thread segments, a second screw thread on an inner surface of the skirt of the closure, said second screw thread comprising four or several other thread segments, said first and second screw thread being designed to enable a user to attach, remove and reattach the closure in a sealing position on the opening by rotating the closure on the opening.

Such a container can e.g. be a drinking glass or a cup. The present invention allows different designs of drinking glasses and cups to be adapted to secure, leak-proof and possibly also pressure-tight closures. The closure unit according to the present invention is also suitable for various other containers with wide mouths, especially for storing materials under pressure.

Current commercially mass-produced beverage containers use threads on the container neck and a closure that also has threads. The threads comprise a single, mainly continuous thread part on the container neck, with a small pitch angle of the thread, typically less than 5°. The small pitch angle is necessary to ensure that the closure does not unscrew spontaneously. The small pitch angle also provides the necessary exchange to achieve an airtight compression seal between the closure and the container neck when the closure is screwed onto the container neck. The small pitch angle of the threads also means that the closure typically needs to be rotated more than 360° to completely disconnect it from the container neck.

Disadvantages of these small-pitch threads include the labor-intensive rotation needed to remove and attach the closure to the neck, excessive use of casting material to form the long threads, and unreliable separation of tamper-revealing rings from the closure skirt due to the small pitch angle of the gangs. The difficulty of attaching the closure to the neck is particularly severe for beverage containers, since the very small angle threads required for large openings are easily crossed. Furthermore, the problem of using a large amount of molding material is particularly serious for the large opening of a beverage container.

International patent application WO95/05322 describes an improved pressure-proof closure for carbonated beverage containers. The application describes closure devices for containers with substantially continuous threads that define a substantially continuous helical thread path, although the pitch of the helix may vary. The closure can be moved from a fully disengaged to a fully secured position on the container neck by rotation of 360° or less. The threads of the neck or the closure are provided with mutual elements for engagement to prevent or limit rotation of the closure in an unscrewing direction after a central position when the closure is under an axial pressure in a direction away from the container neck; the neck and closure are designed and arranged to effect venting of gas from the container neck at least when the closure is in the center position. This pressure safety feature prevents the closure from blowing out uncontrollably once the unscrewing of the closure from the container neck has begun. It thus allows the use of shorter threads, with steeper pitches or multi-state threads on the container and the closure unit, thereby making the unit much more elderly and child-friendly without reducing the pressure safety. WO97/21602 and WO99/19228 describe improved versions of the devices of WO95/05322.

The closure assembly for the beverage container exemplified in WO95/05322 has short, projecting thread segments on the capsule and longer (but still short relative to conventional low-pitch closures) projecting thread segments on the container neck. This device is common, partly because the requirements for high-speed injection molding of the capsules, according to which the capsules must be "dumped" out of a (preferably) single die with minimal deformation.

Interestingly, the various screw-top formats for beverage containers have not yet completely replaced glass bottles with crown closures, despite the fact that crown closures require a bottle opener to open, and cannot be reattached to the neck of the bottle in an airtight manner, thereby necessitating the consumption of the entire contents of such a bottle after opening.

It is believed that one of the reasons for the continued use of crown closures is that they are better suited for consumption directly from the bottle due to the relatively smooth surfaces of the bottle neck being more comfortable between the consumer's lips. This characteristic will be referred to as "ease of use" for the bottleneck. In contrast, container necks for screwing on have neck rings that represent a relatively uneven or abrasive surface for the lips.

It is an object of the present invention to arrive at improved screw-on closure units for beverage containers. The present invention is particularly applicable to beverage containers containing beverages, including carbonated beverages.

The threaded closure unit according to the invention is characterized by the fact that the first thread segments are shorter than the other thread segments, that the other thread segments are each formed by one or more projecting parts arranged radially from each other, and which project radially for no more than approximately 60° around the closure skirt, and the second thread segments define a substantially continuous, helical thread path along which the first thread segments are moved from a substantially fully disengaged to a substantially fully secured position for the closure of the container,

the assembly comprising complementary locking elements on the container opening and closure which resist unscrewing of the closure from the fully engaged position on the container after the closure has been secured or re-secured on the container, until a predetermined minimum opening torque is exerted.

Normally, the opening of a beverage container has an inner diameter of at least about 3 cm, preferably from about 4 cm to about 10 cm, and more preferably from about 5 cm to about 8 cm. The opening is normally mainly cylindrical. The present invention is also applicable to other wide mouth containers having openings of these preferred diameters.

In certain designs, the beverage container is mainly tubular, e.g. it can be in the form of a drinking glass. In certain designs, the opening at the top has an area of at least about 50% of the area of the bottom of the container, preferably at least about 80% of the area of the bottom of the container, and in certain designs, the area of the opening at the top of the container is greater than the area of the bottom of the container.

The drinking container is preferably formed of thermoplastic material, i.e. of a molded polymer, but it can be formed of glass. The threaded opening is preferably formed integrally with the beverage container.

The closure is preferably formed from injection-molded thermoplastic, and it is a particular advantage of the present invention that the closure can be easily produced by high-speed injection molding, as will be described in more detail below.

Preferably there are at least four of said first thread segments. In the designs with larger openings, there may in particular be eight, twelve, sixteen or more of the first thread segments. The number of second thread segments is typically the same as the number of first thread segments. Preferably, this leads to the number of thread starters being equal to the number of first thread segments, or preferably at least two thread starters, more preferably at least four, most preferably eight, twelve, sixteen or more thread starters.

The first thread segments on the opening are shorter than the other thread segments. That is they extend radially around the opening at a smaller angle than the angle through which the other thread segments extend around the closure skirt. The first thread segments do not extend all the way around the opening, and normally they do not overlap around the opening. Preferably, at least one of the first thread segments extends circumferentially from about 1 to about 30° around the opening, more preferably from about 2 to about 15°, more preferably from about 3 to about 10°, and more preferably all of the first thread segments extend as . Preferably, the maximum length of each first thread segment is from about 2 to about 20 mm, more preferably from about 4 to about 15 mm, more preferably from about 6 to about 12 mm. Preferably, at least about 40% of the circumference of the opening is without the first threaded segments, more preferably from about 50% to about 95% of the circumference of the opening is without the threaded segments. The absence of the threaded segments from the majority of the circumference of the opening increases the ease of use of the opening.

Preferably, all the first thread segments have essentially the same shape and design, whereby the number of thread starts can be equal to the number of the first thread segments.

The term "first threaded segment" typically refers to an elongated protrusion with a pitch on the outside of the opening. It preferably does not refer to a single protruding knob or stick. The average pitch of the first thread segment surfaces is preferably from about 5° to about 25°, more preferably from about 10° to about 20°. The upper and lower surfaces of the first thread segments may have different pitches, and the pitches along one or the other of said surfaces may also vary. Preferably, at least one of said surfaces has at least one region of constant pitch extending at least about 2 mm, preferably about 5 mm or about 20 mm around the opening. E.g. the first thread segment may be a short helical thread segment with rounded ends, similar to the thread segments of the closure caps described in detail in WO95/05322 or WO97/21602.

The first thread segments can be mainly triangular, rectangular, rounded or chamfered rectangular, or trapezoidal in cross-section along the longitudinal axis of the container. Preferably, the first thread segments are smoothed, ie at least one edge of the segments is shaped to represent a rounded or chamfered cross-section along the longitudinal axis of the container rather than a triangular, rectangular or trapezoidal cross-section between the side of the segment and the top of the segment. Preferably, substantially all edges of the segment are smoothed in this way. Preferably, this leads to an increased radius of curvature between the top of the segment and the side of the segment relative to prior art. E.g. the radius of curvature may be at least 0.5 mm, more preferably at least 1 mm or 2 mm. Preferably, the cross-section of the segments along the longitudinal axis of the container is a substantially continuous curve, such as a semicircular or sinusoidal curve. This smoothed profile improves the usability of the closing of the opening thread.

Preferably, the maximum radial height of the first threaded segments above the cylindrical base of the threaded termination of the opening is greater than 0.1 mm, more preferably greater than 0.2 mm and even more preferably from 0.5 to 3 mm, most preferably from 1 to 2 mm. Preferably, the width of the first thread segments (measured along the longitudinal axis of the container) is from 1 mm to 6 mm, more preferably from 2 mm to 4 mm. The use of such relatively large and tall thread segments helps to make it possible to produce a user-friendly neck design to which a suitable screw top can be attached and reattached in a pressure-proof manner. Nevertheless, the small length of the first thread segments and the usually rounded or even cross-section of the first thread segments enable the relatively high thread design of the opening to be made user-friendly, and in particular made comfortable against the lips of a user who drinks directly from the opening.

Preferably, the other thread segments on the inside of the wearer skirt define a

substantially continuous helical thread path along which the first thread segments are moved from a substantially fully disengaged to a substantially fully secured position of the closure of the threaded opening. That is that the first and second threads do not engage in a stepped manner similar to a bayonet closure (which is normal for short-threaded segments), but rather in a regular continuous helical manner. In other words

the pitch of the thread path is normally less than 90° throughout its length. It will be understood that the pitch of the helix need not be constant. Preferably, the average pitch of the helical thread path is from 5 to 20°.

The continuous thread path makes the device particularly easy to close for the elderly and weak, or for children. In contrast, the bayonet type threads described in US-A-5135124 require a relatively complex, step-by-step manipulation to secure the closure to the opening, with the result that the closure is often inadequately secured. Furthermore, it is extremely difficult to construct a tamper-evident ring for the closure that separates reliably and easily upon opening a bayonet-type closure assembly. Finally, a continuous thread is easier for physically weak people to turn down against the pressure from inside the container than a bayonet thread.

The other thread segments are not bayonet type thread segments. The other thread segments extend around the closure skirt a sufficient length so that a top part of a thread segment is close to a bottom part of another thread segment, i.e. sufficiently close to the adjacent thread segment that the gap between them is too narrow to allow one of the first thread segments to pass through vertically. In certain designs, respective top and bottom portions of adjacent second thread segments are circumferentially overlapping.

Preferably, at least one of the other thread segments extends at least 30°, preferably at least 45° around the closure skirt, more preferably at least 60° around the closure skirt. A thread gap is defined between said top and bottom part of the thread segments. One of the first thread segments is moved through this thread gap as the closure is screwed on or off the container opening.

Preferably there are eight, twelve or sixteen of the other thread segments. Preferably, the first and second thread segments define a four-start, eight-start or twelve-start substantially continuous and rapidly rising thread path.

Preferably, the closure can be moved from a fully released to a fully engaged position on the opening (or vice-versa) with a single, smooth rotation of about 180° or less, more preferably about 90° or less, and most preferably about 45° or less .

Preferably, the maximum radial height of the second thread segments around the cylindrical surface of the closure skirt is greater than about 0.1 mm, more preferably greater than about 0.2 mm and even more preferably from about 0.5 to about 3 mm, most preferably about 1 to about 2 mm. Preferably, the width of the second thread segments (measured along the longitudinal axis of the closure skirt) is from about 1 mm to about 6 mm, more preferably from about 2 mm to about 4 mm.

The other thread segments are each formed by one or more radially spaced, projecting portions, each said portion extending radially no more than about 60° around the closure skirt, preferably no more than about 45° around the closure skirt, more preferably from about 2° to about 35 ° around the closing skirt. The protruding parts are preferably arranged radially apart with gaps extending radially from 0 to about 10°, preferably from about 0.5° to about 2°. Preferably, the width of the gaps is from about 0.1 mm to about 5 mm, more preferably from about 0.5 mm to about 2 mm. In other words, the second thread is preferably a broken or interrupted thread with several gaps in each thread segment, but the gaps are sufficiently radially narrow not to interfere with the action of the other thread segments. That is that the other thread segments still define a substantially continuous helical thread path between them. This requires that the gaps in the second thread segments (in addition to the gaps between the second thread segments) are radially narrower than the first thread segments.

Preferably, every second threaded segment is formed of at least two parts, preferably at least three or four parts, and this preferably results in at least one or preferably at least two or three gaps in the threaded segment. The presence of the gaps in the second thread segments can improve gas venting through the second thread when pressurized containers are opened. The closure caps are easier to dump out of an undivided mandrel during high-speed manufacturing, due to the fact that the broken threads provide less resistance to radial expansion of the closure skirt.

Preferably, at least one of the other thread segments also has an equalized cross-section. The cross-section of the second thread is preferably similar to the cross-section described above for the first thread segments. It will be understood that this can lead to a better fit between the first and second thread segments, e.g. if they have adapted cross-sectional shapes parallel to the axis of rotation. Furthermore, tapered or smoothed threads on the closure make it easier to dump the closure out of a casting mandrel, thereby contributing to the high-speed production of the closures by injection molding without the necessity of castings in several parts.

The present invention is applicable to a large number of beverage containers of any shape where ease of use is desirable, including beverage containers for both carbonated and non-carbonated beverages. The present invention is applicable to container closure units of molded thermoplastic, and also to closure units for glass or metal containers, and to combinations thereof (eg a glass container with a metal or thermoplastic closure).

Preferably, the container closure unit according to the present invention further comprises complementary locking means on the container opening and the closure which resists unscrewing the closure from the fully connected position on the opening after the closure has been attached or reattached to the opening until a predetermined minimum opening torque has been exerted. These elements make it possible for threads with a steeper pitch and free running (parallel) threads to be used without the risk of the closure being unscrewed spontaneously. The use of threads with a steeper pitch again makes it possible to use wider and higher thread segments within the size and height limitations of a normal neck termination.

Preferably, the locking means on the opening comprise a projection or a recess for engagement with a complementary projection or recess on the closing skirt. More preferably, the protrusion or hollowing out of the opening is smoothed as previously defined herein.

More preferably, the locking means comprise a longitudinal locking rib on the container opening, and a complementary locking ramp on the skirt part of the closure, in which the locking rib rests against a holding edge on the locking ramp when the closure is fully connected to the opening. In alternative preferred designs, a locking recess such as a longitudinal groove may be provided in one or more of the first or second threaded segments, and a longitudinal locking rib is provided on the other of the opening or on the skirt portion of the closure, whereby the locking rib is inserted into the recess in the threaded segments at the fully connected and sealing position of the closure on the opening. Locking means of this type are described in detail in WO91/18799 and WO95/05322.

The complementary locking means provide several important advantages. First, they prevent inadvertent repulsion of the closure from the fully engaged and sealing position of the container due to pressure from inside the container. This also allows the use of threads with a steeper pitch. Furthermore, the locking means provide a positive "click" when the fully connected and sealing position of the closure is reached, thereby giving the user a positive indication of this position. This helps to ensure that exactly the correct degree of pressure is applied between the container and the closure to achieve an effective, airtight closure.

Preferably, the container closure unit according to the invention is a unit for a carbonated beverage, wherein the container further comprises mutually engaging elements on the container opening and the closure to block or limit rotation of the closure in a unscrewing direction past a middle position when the closure is under axial pressure in a direction away from the container. This is the so-called pressure safety feature which is intended to prevent the closure from uncontrollably unscrewing or being ejected as it is removed from a container under pressure. Preferably, the preferred designs of this pressure safety feature are as described in WO95/05322, WO97/21602 and WO99/19228.

Preferably, the first and second screw threads are constructed and arranged to allow axial movement of the closure relative to the container opening at least when the closure is in said intermediate position, and preferably the engageable elements are adapted to engage with each other when the closure is axially moved in a direction away from the opening, e.g. by axial pressure from inside the pressurized container. More preferably, the mutually engaging elements are designed and arranged not to engage with each other when the closure is axially moved in an inward direction towards the container at the middle position, e.g. when the closure is screwed down on the container opening.

Preferably, the mutually engaging elements comprise a step or recess formed in the upper surface of one of the second screw thread segments, to form a first abutment surface against which a second abutment surface of one of the first screw thread segments rests, to block or prevent rotation of the closure in a unscrewing direction at the said intermediate position when the closure is under axial pressure in a direction away from the container. (The term "upper" in this context means closer to the base of the closure, in other words further from the open end of the closure). More preferably, the second thread segment comprises a first thread part with a first longitudinal cross-section and a second thread part with a second longitudinal cross-section narrower than the first cross-section, whereby the first thread segment abuts the second thread part. The relatively wide first cross-section is preferably adjacent to the surrounding overlapping portion of the other thread segments, leading to a relatively narrow thread gap in that area.

The units according to the present invention further preferably comprise additional means for forming a pressure-tight seal between the container and the closure. In certain embodiments, the sealing means includes a compressible liner on the inside of the base portion of the closure to abut against a lip of the container opening. Preferably, the sealing liner is formed from a compressible elastomer. A circumferential sealing rib may be provided on the lip of the opening, or on the inside of the base of the closure below the sealing liner, to optimize compression of the elastomer to achieve a pressure-tight seal. However, preferably the lip of the container is smooth and rounded to optimize its ease of use.

In other designs, the sealing means may comprise a cylindrical sealing plug which projects eccentrically and on the inside of the closing skirt and which forms a pressure-tight seal against the inside of the container near the opening.

Preferably, the first and second threads on the container opening and closure are variable pitch threads, preferably as described in WO97/21602. Preferably, the pitch of a unscrewing thread path defined by the first and second thread segments is relatively smaller in a first region and relatively larger in a second region displaced from the first region in a unscrewing direction. The pitch of the thread path in the first region is preferably substantially constant. The first region normally includes the position at which the closure is sealed on the container. Preferably, the first region extends approximately 2° to 40°, preferably 5° to 20° around the circumference of the container opening or closure skirt. Preferably, the pitch of the lower thread surface in the first region is about 1° to 12°, more preferably 2° to 8°.

Preferably, the second area is adjacent to the first area of the thread path. Preferably, the pitch of the helical thread path in the second region is substantially constant, and the second region preferably extends from about 2° to about 35°, preferably from about 5 to 15° around the circumference of the container neck or closure skirt. Preferably, the pitch of the thread path in the second region is about 15° to 35°.

The use of a thread with a variable pitch makes it easy to combine quick screw threads with a steep average pitch that is elderly and child friendly with pressure safety. A problem that can occur with quick release threads is that they have a steep pitch, which causes them to tend to be driven out of the fully secured position on the container when the container is pressurized. This problem can be solved by using bayonet threads, but the use of bayonet threads leads to several different problems, as described above. In contrast, the variable pitch threads solve the problem of dislodgement of the closure under pressure, retaining all the advantages of continuous quick screw threads.

Preferably, the helical unscrewing thread further comprises a third area adjacent to the second area, in which the third area has a relatively small pitch. Preferably, the third area has a relatively constant pitch, preferably in the range of 1 to 12°, more preferably 2 to 8°. The third region preferably includes the position of the closure of the opening when the closure is blocked at the middle gas vent position. The relatively small rise to the third area reduces the tendency of the closure to override the blocking means at high gas vent pressures.

In certain designs, the closure assembly includes a recess in the inner surface of the closure skirt, the recess being located between and circumferentially overlapping two of the plurality of other thread segments to increase the cross-sectional area provided for gas venting between the other thread segments.

It has been found that the thread gap between overlapping portions of adjacent other thread segments may have a cross section that is too small for optimal gas ventilation in all cases. The hollowing solves this difficulty by increasing the cross-section of the thread gap to increase the rate of gas vented through the thread gap.

The increased cross-sectional area of the vent path in the surrounding overlapping areas of the second thread allows for faster venting of pressure from inside the container, thereby reducing the time that the closure is blocked at the center position as venting occurs, without any loss of pressure safety.

In these designs, the recess may comprise an elongated groove extending around the closure skirt between the other thread segments in the aforementioned overlapping areas. Preferably, the elongated groove extends substantially parallel to the helical thread path. Preferably, the hollowing comprises an elongated groove on the inside of the closing skirt. Preferably, the longitudinal cross-sectional area of the recess is from 5% to 50% of the average longitudinal cross-sectional area of the other thread segment portions adjacent to the recess.

Specific designs of the closure units for beverage containers according to the present invention will now be described in more detail by way of example, with reference to the attached figures, where: Fig. 1 shows a longitudinal sectional sketch of a beverage container comprising a closure unit according to the present invention invention, with the closure in the fully engaged position on the container opening, and with a tamper-evident ring attached to the closure, Fig. 2 is a longitudinal sectional view of the beverage container of Fig. 1, with the closure

reattached to the container opening, and with a tamper-revealing ring removed, and

Fig. 3 shows a detail of the closure area of the cut in fig. 1, with the first and second

the threaded segments on the back of the unit shown in the X-ray drawing.

With reference to fig. 1 and 2, this design is a drinking container 1 in the form of a drinking glass with a bottom 2 of diameter around 5 cm and a top 3 of inner diameter around 7 cm and a tubular body 4 of circular cross-section. The aesthetic and practical appeal of such a liquid packaging format is clear, but it has not been possible to form a reliable closure device for such wide mouth containers to date.

The main features of this device are similar to those of the device described in International Patent Applications WO95/05322 and WO97/21602 and WO99/19228. However, it is important to note that the threads on the closure and container opening are reversed in the present invention relative to the closure units described in these applications. That is, the previous applications describe in detail units with short thread segments in the closure skirt and longer thread segments on the neck, whereby the present invention only provides for short thread segments on the container opening and longer thread segments on the closure skirt.

The unit is particularly suitable for storing carbonated drinks such as beer. It includes an opening 10 at the top of the container and a closure 12. Both the container and the closure are formed of plastic material. The container is preferably designed by injection moulding, pressure forming and/or thermoforming of polyethylene terephthalate or polystyrene in the manner well known for such containers. The closure is preferably designed by injection molding of polypropylene.

With reference to fig. 3, the container opening 10 is designed with an eight-start first screw thread formed by eight first thread segments 18, as shown in fig. 3. The first thread segments 18 are short thread segments extending about 10-15 mm around the opening and having a lower surface with a relatively small pitch of about 6° and an upper surface with an average pitch of about 13.5°. (The term "upper" in this case means closer to the open end of the container). The first threaded segments 18 represent a substantially trapezoidal cross-section along the axis of the container. The container has a rounded lip to increase ease of use for the opening.

With reference to fig. 1 and 3, the closure 12 comprises a base part 14 and a skirt part 16. The closure skirt 16 is formed with a second screw thread formed by eight other thread segments 20, each with a lower thread surface 22 and an upper thread surface 24. (The term "upper" in this case meaning closer to the base of the closure, in other words further away from the open end of the closure). The upper and lower second thread surfaces 22, 24 give the thread segments mainly trapezoidal side edges which correspond to the shape of the first thread segments. A substantially continuous, approximately helical thread gap 26 is defined between overlapping areas in said upper and lower surfaces 22, 24 of adjacent second thread segments 20.

An important feature of this unit is the profile of the upper surfaces 24 of the second thread segments 20, which is described in greater detail in International Patent Application WO97/21602. The upper thread surfaces 24 in a first, upper region 28 have a substantially constant pitch of only about 6°. The upper region 28 adjoins an intermediate region 30 with a substantially constant, much higher pitch of about 25°. The average pitch of the helical thread path defined by the other thread segments 20 is 13.5°.

The other thread segments 20 also include a pressure safety feature similar to that described in international patent application WO95/05322. In short, the lowest area of the second threaded segment 20 defines a step to abut against an end of the first threaded segments 18 and block the unscrewing of the closure 12 from the opening 10 when said threaded segments 18 abut against the upper surface 24, in other words when there is a net force on the closure in an axial direction away from the container. A third area 34 on the upper surfaces 24 of the other thread segments placed adjacent to the step 32 also has a low pitch of approximately 6°.

The closure assembly is also designed with matching locking elements 38 on the container opening and closure to block unscrewing of the closure from the fully engaged position on the container unless a minimum unscrewing torque is applied. These locking elements comprise four locking ribs placed equally radially apart from each other on the opening, and four half ramps placed equally radially apart from each other on the inside of the closing skirt 16. The ramps comprise a radially beveled outer surface and a radially projecting holding edge against which the rib on the closure abuts when the closure is complete in engagement with the opening. The corresponding locking means can be as described in international patent application W091/18799. However, the locking rib is on the container and not on the closure in this design, which also helps improve the usability of the container neck design, especially with a suitable offset rib.

The closure unit also includes means for forming a gas-tight seal between the closure and the container. This means may comprise a gas-tight elastomeric sealing liner which is compressed against the lip of the container. Optimal sealing is preferably achieved when the elastomeric sealing liner is compressed to between 30% and 70% of its original thickness. In other designs, the seal can be achieved without the need for any lining, e.g. by compression of suitably configured surrounding sealing plug, ribs and/or fins on the closure capsule against the opening. Suitable sealing devices are described in international patent application WO02/42171.

The second threaded segments 20 terminate at their lower end in a projecting part which defines a longitudinal shoulder 72 which forms a first stopper, against which a second end 74 of the first threaded segments 18 can lie to thereby block against overtightening of the closure.

The closure assembly also optionally includes a tamper-evident security feature. This includes a tamper-detecting ring 50, which is initially designed integrally with the skirt 16 of the container closure 12 and is connected thereto via fragile bridges. The tamper-detecting ring 50 comprises a plurality of integrally shaped, flexible, radially inwardly directed retaining tongues. A surrounding retaining lip 56 is provided on the container opening 10. Detent protrusions (not shown) may also be provided on the container below the surrounding retaining lip 56 and radially distributed around the opening, to block rotation of the tamper-revealing ring 50 on the opening 10 in a unscrewing direction. However, it may be preferred to smooth out or omit the latch projections to improve the usability of the container opening design. The construction and operation of the tamper-evident ring is as described in International Patent Application WO94/11267.

In use, the closure 12 is attached to the container opening 10 by screwing it down in the usual way. The closure 12 can be moved from a fully disconnected position to a fully connected position on the container by rotating approximately 45°. When the closure is screwed down, there is normally a net axial force applied by the user to the closure on the container, and respectively the first thread segments 18 abut against and slide along the upper surfaces 22 to the projecting parts of the second thread segments 20 on the closure skirt. It can thus be seen that the first thread segments follow an essentially continuous path along a helix with variable pitch. The first and second threads are freewheeling, that is, there is essentially no frictional torque between the thread segments until the fully engaged position is approached. These features with a 45° closure rotation, mainly continuous thread path and free-running threads make the closure extremely easy to fasten and refasten, especially for the elderly and people with gout, or children.

As the closure approaches the fully engaged position on the container opening 10, several things occur. First, the tamper-detecting ring 50 begins to slide over the retaining lip 56 of the container opening. The retaining tabs of the tamper-detecting ring 50 are bent radially outward to enable the tamper-detecting ring to pass over the retaining lip 56 without excessive radial stress in the fragile bridge.

Second, the locking ribs on the container opening slide up along the outer inclined surface of the retaining ramps on the closure skirt 16. The slight inclination of the inclined surfaces, together with the elasticity of the closure skirt 16, means that relatively little additional torque is required to cause the locking ribs to slide up along the inclined surfaces.

Third, the initial engagement between the sealing liner or other sealing means in the container closure base and the sealing lip 48 on the container results in a net axial force on the closure in a direction away from the container. This pushes the thread segments 18 out of engagement with the lower surfaces 22 of the projecting portions of the second thread segments 20 and into engagement with the upper surfaces 24 of the projecting portions of the second thread segments 20. More specifically, the first thread segments 18 are brought into engagement with the upper regions 28 on the projecting parts of the upper thread surfaces 24. Continued rotation of the closure in a downward screwing direction causes the first thread segments 18 to be moved along the upper regions 28 until the last, fully connected position shown in fig. 3 has been reached. The low pitch of the upper surfaces 28 means that this further rotation causes a large force ratio (engagement) to press the sealing liner against the sealing rib 48 to achieve an effective gas-tight seal.

When the fully engaged position of the closure 12 on the container opening 10 is reached, the locking ribs snap over the top of the respective inclined surfaces 40 and into engagement with the steep retaining surfaces of the barbed ramps. In the same position, the other ends 74 of the first threaded segments 18 can engage with the stop shoulders 72 on top of the other threaded segments, thereby blocking further screwing of the closure which may damage the threads and/or overcompress the sealing liner.

When the closure 12 is in the fully connected position on the container opening 10, the upper surfaces of the first threaded segments 16 abut against the upper areas 28 of the upper threaded surfaces 24 of the protruding parts of the second threaded segment 20, as shown in fig. 3. The upper surface of the first threaded segments has a low pitch to conform to the upper regions 28, to maximize the contact area between the protruding parts in the regions 28, thereby distributing the axial force applied by the closure as evenly as possible around the container opening . Because of the low pitch in the areas 28, relatively little of the axial force coming from the container due to the pressure inside the container is converted into unscrewing rotational force of the device between the thread surfaces in this position. This greatly reduces the tendency for the closure to unscrew spontaneously under pressure. Spontaneous unscrewing is also prevented by the system between the locking ribs and the holding edge of the locking ramps. An important advantage of the device is that the reduced tendency to unscrew spontaneously due to the low pitch of the threads in the lower regions 28 means that the minimum torque for opening the locking elements 38 can be reduced without risk of the closure blowing loose spontaneously. This makes the closure easier to remove for the elderly or people with gout, or by children, without reducing the pressure safety of the closure.

When in use, the closure is removed from the container by simply unscrewing it. An initial, minimum unscrewing torque is required to overcome the resistance of the locking elements 38. Once this resistance has been overcome, it is almost not necessary to apply any torque to unscrew the closure. The internal pressure on the inside of the container applies an axial force to the closure in a direction away from the container opening, and the result is that the first threaded segments 18 slide along the upper surface 28 of the protruding parts of the second threaded segments 20 as the closure is unscrewed. The first threaded segments initially slide along the upper regions 28, and then along the middle regions 30 with a steep rise on the upper surface of the second threaded segments 20. The first threaded segments 18 then come into contact with a lower protruding part 32 of the second threaded segments 20 In this position, further unscrewing of the closure is blocked as gas ventilation takes place along the thread paths 26. It should also be noted that in this middle gas venting position, the first thread segments 18 primarily abut against the area 34 of the upper surface of the second thread segments 20. The low the rise in this area means that relatively little of the axial force on the closure is converted into unscrewing torque, thereby reducing the tendency for the closure to override the pressure safety feature and blow loose.

When venting from the inside of the container is complete, so that there is no longer an axial upward force on the closure, the closure can drop down to bring the threaded segments 18 into contact with the lower surfaces 22 of the other threaded segments 20. In this position, unscrewing can continue to completely disconnect the closure from the container.

The above design has been described by way of example only. Many other embodiments of the present invention that are within the scope of the appended claims will be apparent to those skilled in the art. In particular, the present invention is not limited to closure units for beverage containers, or to containers made of molded thermoplastic.

Claims (23)

1. Threaded container and closure unit, said unit comprising: a container opening (10) with an inner diameter of at least approximately 4 cm, a closure (12) for said opening, the closure having a base part (14) and a skirt part ( 16), a first screw thread on the opening, said first screw thread comprising four or more first thread segments (18), a second screw thread on an inner surface of the skirt of the closure, said second screw thread comprising four or more second thread segments (20), said first and second screw threads are designed to enable a user to attach, remove and reattach the closure in a sealing position on the opening by rotating the closure on the opening, characterized in that the first thread segments (18) are shorter than the other thread segments (20), that the other threaded segments (20) are each formed by one or more projecting parts arranged radially apart, and which project radially for no more than approximately 60° around the closing skirt, and the the second thread segments define a substantially continuous helical thread path along which the first thread segments (18) are moved from a substantially fully disengaged to a substantially fully secured position for the closure of the container, the assembly comprising complementary locking elements (38) on the container opening (10) and the closure ( 12) which resists unscrewing of the closure from the fully engaged position on the container after the closure has been secured or re-secured on the container, until a predetermined minimum opening torque is exerted. 2. Threaded container and closure unit according to claim 1, wherein at least one of the first threaded segments (18) extends circumferentially from 5 mm to 30 mm around the container neck. 3. Threaded container and closure unit according to claim 2, wherein at least one of the first threaded segments (18) extends circumferentially from 10 mm to 20 mm around the container neck. 4. A threaded container and closure assembly according to any preceding claim, wherein at least one of the first threaded segments (18) has an upper or a lower surface with an average pitch of from 5° to 25°. 5. A threaded container and closure assembly according to any preceding claim, wherein at least one of the first threaded segments (18) has an upper or a lower surface with a region of constant pitch extending at least 10 mm around the container opening. 6. A threaded container and closure assembly according to any preceding claim, wherein at least one of the other threaded segments (20) extends at least 45° around the closure skirt. 7. A threaded container and closure assembly according to any preceding claim, wherein at least one of the other threaded segments (20) is formed from two or more projecting parts. 8. A threaded container and closure assembly according to any preceding claim, wherein the radially spaced projecting portions each extend less than about 45° around the closure skirt. 9. A threaded container and closure assembly according to any preceding claim, wherein the radially spaced projecting portions are radially spaced apart radially from 0 to 10°. 10. A threaded container and closure assembly according to any preceding claim, wherein the maximum radial height of the first and/or second threaded segments is from about 0.5 to about 3 mm. 11 A threaded container and closure assembly according to any preceding claim, comprising further mutually engaging elements on the container opening (10) and the closure (12) to block or limit rotation of the closure in an unscrewing direction past an intermediate position when the closure is under axial pressure in a direction away from the container. 12. A threaded container and closure assembly according to any preceding claim, wherein the average pitch of said helical thread path is from 5 to 20°. 13. A threaded container and closure assembly according to any preceding claim, wherein the second threaded segments (20) define at least one recess for receiving the first threaded segments, the recess being substantially helical and extending more than 30° around the closure skirt. 14. A threaded container and closure assembly according to any preceding claim, wherein at least one of the second threaded segments (20) has a leveled cross-section. 15. A threaded container and closure assembly according to any preceding claim, wherein the first threaded segments (18) have a cross-section along the longitudinal axis of the assembly that is rounded, chamfered, trapezoidal or triangular. 16. A threaded container and closure assembly according to any preceding claim, wherein the closure (12) is movable from a fully released to a fully engaged position on the container opening (10) by a single smooth rotation of about 90° or less. 17. A threaded container and closure assembly according to claim 16, wherein the closure is movable from a fully released to a fully engaged position on the container opening by a single smooth rotation of about 60° or less. 18. A threaded container and closure assembly according to claim 17, wherein the closure is movable from a fully released to a fully engaged position on the container opening by a single smooth rotation of about 45° or less. 19. A threaded container and closure assembly according to any preceding claim, wherein the locking means (38) comprises a projection or recess for engagement with a complementary projection or recess on the closure skirt. 20. Threaded container and closure unit according to any preceding claim, wherein the container (1) has a bottom (3) and tubular side walls (4), the cross-sectional area of the opening (1) being at least 50% of the cross-sectional area of the bottom ( 3). 21. Threaded container and closure unit according to claim 20, in which the container (1) is formed from a material selected from the group comprising thermoplastics, glass, metal and combinations thereof. 22. Threaded container and closure unit according to claim 20 or 21, in which the container (1) contains a beverage. 23. Threaded container and closure unit according to claim 22, wherein the beverage is carbonated.